By wireless handset, it is meant a cellular phone using radio waves to enable a party to make phone calls to another party. There are various well-known cellular communication technologies. The GSM (Global System for Mobile communications) system which uses time division multiple access technology and the UMTS (Universal Mobile Telecommunications System) which uses code division multiple access technology are two examples of such technologies.
With the advanced development of wireless communication technologies, it is now possible to support multiple wireless communication subscriptions using different or the same communication technologies in one communication apparatus.
In some handsets able to handle two communications, the same baseband and radiofrequency circuitry is used to access two independent cellular networks. Therefore, there is a general problem of management of this unique resource when both cellular networks need to establish a communication with the handset at the same time.
Particularly, when the handset is in idle mode, it needs to listen regularly to the networks to be informed of any incoming call. However, as the timing of each network may be totally independent, a conflict occurs when the handset has to listen to both networks at the same time. In this situation, the handset may miss an incoming call.
Technically speaking, the handset in idle mode can be reached by the network via the Paging Channel (PCH). The handset regularly (i.e. periodically) monitors the PCH. Meanwhile, the monitoring moments are referred to as paging occasions. In GSM or UMTS, the handset, also known as the mobile station (MS) or the user equipment (UE), may use discontinuous reception (DRX) during the idle mode to reduce power consumption. When DRX is used, the base station, i.e. the network, may transmit the paging messages periodically at the paging occasions and thus, the handset can receive the paging messages carried in the paging channel (PCH) burst at the paging occasions. The paging occasion defines the time for the handset to wake up and receive the PCH burst. After receiving the paging message, the handset may decide whether or not to sleep again by checking a flag (for instance, the “Page Indicator (PI)” in UMTS or the “MS Identity IE” in GSM) in the paging message. If the flag reveals that the handset is now being paged, the handset may initiate a process to receive the incoming call. Otherwise the handset may decide to sleep again and wake up at its next paging occasion.
When the radio transceiver module of a handset is shared between two identity cards, i.e. two network subscriptions, the handset may monitor only one wireless network for a specific time interval. As a result, listening to a paging message for one accessible wireless network during a wake-up time slot, i.e. paging occasion, may hinder listening for another accessible wireless network. Paging collisions occur when at least two paging occasions corresponding to different wireless networks respectively are present in the substantially same wake-up time slot (e.g. overlapping or identical time slots).
The patent application US 2009/0215473 discloses a communication apparatus in which a first subscriber identity card camps on a first cell and a second subscriber identity card camps on a second cell. A processor obtains information regarding first paging occasions distributed within a predetermined time interval for the first subscriber identity card, obtains information regarding second paging occasions distributed within the predetermined time interval for the second subscriber identity card, detects a forthcoming time slot of the predetermined time interval in which one of the first paging occasions collides with one of the second paging occasions, determines listening to one of the first cell and the second cell in the detected time slot, and notifies of the determination to the radio transceiver module so as to direct the radio transceiver module to listen to the determined cell to receive a corresponding paging message from the determined cell in the detected time slot.